Stock classes explained: what your startup equity actually is

Quick answer: share classes and award types are different things

Common stock and preferred stock are classes of shares. They describe the rights attached to stock you own. RSUs, ISOs, NSOs and restricted stock are awards — the legal route by which you receive or buy shares, usually common stock. When an employer says "we're offering you equity," your first question is which award you are getting and which share class it ultimately delivers, because that determines what you pay, what you owe in tax and what you could receive in a sale.

Until you know those two answers, a unit count or a headline "value" is not enough to compare offers. Put the grant alongside your salary, bonus, role and location in the startup offer analyzer — it compares cash compensation and flags missing terms, but it does not predict an exit.

What is the difference between preferred and common shares?

Investors buy preferred stock; employees and founders typically hold common stock. They are not the same asset, even when a "price per share" sounds similar, because preferred shares carry rights that common shares lack:

• Liquidation preference: preferred holders generally get their money back — often 1× their investment, sometimes more — before common shareholders receive anything in a sale.
• Participation: "participating" preferred can be paid back and share in the remainder, which further reduces what is left for common.
• Protective rights: preferred stock may carry anti-dilution protection, approval rights over major decisions and board seats that common holders do not have.

In an acquisition, already-owned shares receive whatever their class rights and the deal terms allocate. This is why a headline sale price is not your payout: investors are paid according to their preferences first, and common shareholders split what remains. The acquisitions & payouts guide shows this waterfall with worked examples.

The four award types you are likely to be offered

Restricted stock units (RSUs) are a contractual promise to deliver shares or cash when settlement conditions are met. There is usually no purchase price, but you own nothing until the units vest and settle, and private-company RSUs often require both time vesting and a liquidity event before you receive anything.

Incentive stock options (ISOs) give you the right to buy shares at a fixed exercise price. They can qualify for favorable US federal tax treatment if statutory holding rules are met, but exercising costs real money and can trigger alternative minimum tax before you can sell anything.

Non-qualified stock options (NSOs) work like ISOs mechanically but without the special tax treatment: the spread between the exercise price and the share value is generally taxed as ordinary income when you exercise. NSOs can be granted to contractors and advisers, not just employees.

Restricted stock is actual shares issued up front, subject to forfeiture or repurchase if you leave before vesting. Founders and very early employees most often receive it, sometimes with an early-exercise option feature.

A worked exercise-cost example

Suppose an offer includes 10,000 options with a $2 exercise price. Exercising all of them costs $20,000, before any tax or fees. If 10 million fully diluted shares, including the grant and other included equity awards, is the correct denominator, the award represents 0.1% on that basis, before future dilution. That percentage does not establish a sale payout.

An award of 10,000 RSUs avoids that exercise payment, but its settlement conditions, withholding, share rights and sale restrictions still matter. Do not compare either award by multiplying units by a funding-round share price.

RSUs vs ISOs: how each works and when they vest

How do RSUs work? The company promises you a set number of shares that become yours as you vest. You pay nothing to get them, but they are taxed as income when they are delivered. How do ISOs work? You receive the right to buy shares later at today's fixed exercise price, so they only pay off if the shares become worth more than that price, and you must pay to exercise before you own anything.

When do my RSUs or ISOs vest? Both usually follow the same kind of schedule written in your grant: most commonly four years with a one-year cliff, meaning nothing vests for the first 12 months, then 25% vests at once and the rest vests monthly or quarterly. Private-company RSUs often add a second condition, a sale or IPO, before shares are actually delivered. Your vesting start date, cliff and cadence are in your grant agreement, so ask for it in writing before you accept. In short, RSUs are simpler and lower risk, while ISOs can be cheaper on taxes but require cash and carry more risk.

US tax basics: the rules that actually change your outcome

ISO does not mean tax-free. Qualifying ISOs generally produce no regular federal income tax at grant or exercise, but the exercise spread can count toward the alternative minimum tax (AMT), which can mean a large tax bill on shares you cannot yet sell. To keep ISO treatment you generally must remain an employee through three months before exercise, and you must hold the shares at least one year after exercise and two years after grant for the most favorable treatment. A company may offer a longer post-departure exercise window without preserving ISO status for a later exercise.

RSUs are generally taxed as ordinary income when they settle, based on the share value at that time. Private-company RSUs that settle only on a liquidity event can concentrate years of income into one tax year. Ask how withholding is funded if the shares cannot be sold to cover the tax.

83(b) election: if you receive restricted stock — or exercise options early into unvested shares — filing an 83(b) election with the IRS within 30 days of the transfer starts your tax clock immediately at the current, presumably low, value. It genuinely benefits you when the shares are worth very little today, you expect the company to grow, and you can afford to lose what you paid: if you leave before vesting, the tax you prepaid is not refunded. An 83(b) election is not available for RSUs or ordinary unexercised options, because no property has been transferred yet. Missing the 30-day deadline is generally permanent, so involve a tax adviser before exercising early.

Qualified small business stock (QSBS): under Section 1202, gain on qualifying C-corporation stock can be partially or fully excluded from federal tax, up to a large cap, if requirements are met. The key conditions are that the company is a domestic C corporation with gross assets under $50 million when your shares are issued, you acquire the stock at original issuance (not from another shareholder), and you hold it for more than five years. This benefits founders and early employees who exercise options early at a qualifying company and stay for the long term — the five-year clock starts only when you own shares, not when options are granted, so delaying exercise delays potential QSBS treatment. Recent legislation has changed exclusion percentages and asset limits for newly issued stock, and state rules differ, so confirm the current rules with a tax professional before relying on QSBS in a negotiation.

What is double trigger for stock? Single vs double trigger acceleration

Stock acceleration means some or all of an unvested award vests earlier than its original schedule. It changes timing — it is not a higher share price and not a promise that shares can be sold.

Single-trigger acceleration speeds up vesting after one defined event, usually a change of control such as an acquisition. It is uncommon because buyers dislike inheriting fully vested teams with no incentive to stay. Double-trigger acceleration requires two defined events: a change of control and a qualifying termination — typically dismissal without "cause" or resignation for a defined "good reason" — within an agreed protection window. A sale alone does not satisfy both triggers, and neither does an ordinary resignation.

Who typically gets acceleration: founders and senior executives commonly negotiate double-trigger protection, and some companies extend it to all employees as a policy. Most individual contributors have no acceleration at all unless they ask, which makes it one of the highest-value terms you can negotiate before signing rather than after.

Assume a grant of 20,000 options is 50% vested at acquisition, leaving 10,000 unvested. Under a clause accelerating 50% of the unvested award, a qualifying termination would accelerate 5,000 options — not 50% of the original grant. Accelerated options still require exercise under their terms, and vesting does not remove the exercise price, taxes, investor preferences or sale restrictions.

A "double-trigger RSU" is a different thing: many private-company RSUs use continued service plus a liquidity event as two conditions for vesting or settlement. That describes when you receive the RSUs, not protection if you lose your job after an acquisition. Ask which one your agreement contains.

How awards are treated in an acquisition

Already-owned shares and unexercised awards follow different rules. Shares you own receive whatever their class rights and the deal allocate. Options and unsettled RSUs may be assumed by the buyer, substituted for buyer equity, cashed out or cancelled, depending on the plan, the award's value and the transaction structure. A double-trigger clause may not protect you if the buyer refuses to assume or substitute your award, so ask what happens in that case specifically.

In a low-value sale, common shares behind a large preference stack can receive nothing even after acceleration. Keep acquisition upside separate from the salary and bonus that fund your near-term needs.

The terms to negotiate before signing

• Award type and share class: RSU, ISO, NSO or restricted stock, and which class of shares it delivers.
• Ownership: the fully diluted share count, whether it includes your grant, and the date of that estimate.
• Your cash commitment: exercise price × options for ISOs and NSOs, and how withholding is funded for RSUs.
• Acceleration: single or double trigger, the percentage accelerated, and the definitions of change of control, cause and good reason.
• Protection window: an agreed period before and/or after closing, with clear notice and cure deadlines.
• Award treatment in a sale: what happens if the buyer does not assume or substitute your equity.
• Leaving terms: the post-termination exercise deadline and what happens to vested and unvested awards.

"Before I trade salary for equity, could you confirm the award type, the share class, the fully diluted percentage, my potential out-of-pocket costs, and whether my grant includes double-trigger acceleration if I'm terminated without cause after a change of control?"

This is a starting question, not contract language. For the full negotiation playbook, including vesting cliffs, pro rata rights and the 409A valuation, read the startup equity terms and negotiation guide.